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What speed & direction?

  1. Dec 14, 2007 #1
    I know that this should be simple, but I really can't find out how to do this:
    A pilot needs to fly at 600km/hr on a bearing of 240 degrees to be on time and on course. A wind is blowing from the west at 60km/hr. In what direction and at what speed should she fly her plane to offset the effect of the wind?

    One question I have is when it says "on a bearing of 240 degrees", do you count clockwise or counterclockwise?

    I will greatly appreciate any help.

    Eh, I think I posted in the wrong area, feel free to to move this.
     
    Last edited: Dec 14, 2007
  2. jcsd
  3. Dec 14, 2007 #2

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    Bearings are generally given as the angle that is measured clockwise from north. Now you can use the formula for relative velocity.
     
  4. Dec 14, 2007 #3
    Ok, I think I got it:
    [​IMG]
     
  5. Dec 14, 2007 #4

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    Could you explain the diagram?
     
  6. Dec 14, 2007 #5
    the speed of the plane is 600, so 600sin30 is 300 and 600cos30 is 519.6. The wind coming from the west is 60, so to compensate for that, I add the 60 to the 300 and get 360. Then I use the Pythagorean theorem to get 632.
    Actually, I think I may have done it wrong cause I'm pretty sure I'm supposed to get a different angle.
     
  7. Dec 14, 2007 #6

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    You have to compenste by adding 60 to 600*cos 30. Then you'll get the correct answer.
     
  8. Dec 14, 2007 #7
    So it would be 652.64 with theta=30?
     
  9. Dec 14, 2007 #8

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    I'm leaving that to you. You know how to multiply. I have to do something now.
     
  10. Dec 15, 2007 #9

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    Quite correct. Now find the angle in which the plane has to go.
     
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